Avi Kivity wrote:
> Anthony Liguori wrote:
>> Author: Anthony Liguori <aliguori-r/Jw6+rmf7HQT0dZR+AlfA@public.gmane.org>
>> Date:   Sun Apr 22 20:34:03 2007 -0500
>>
>>     Lazy FPU support for SVM.
>>         Signed-off-by: Anthony Liguori <aliguori-r/Jw6+rmf7HQT0dZR+AlfA@public.gmane.org>
>>
>> diff --git a/drivers/kvm/kvm.h b/drivers/kvm/kvm.h
>> index d1a90c5..4859c32 100644
>> --- a/drivers/kvm/kvm.h
>> +++ b/drivers/kvm/kvm.h
>> @@ -63,6 +63,9 @@
>>  #define FX_BUF_SIZE (2 * FX_IMAGE_SIZE + FX_IMAGE_ALIGN)
>>  
>>  #define DE_VECTOR 0
>> +#define DB_VECTOR 2
>> +#define UD_VECTOR 6
>> +#define NM_VECTOR 7
>>   
>
> This, while a nice cleanup, is unrelated.

I had to add the NM_VECTOR so I moved the others too.  Attached is a 
patch that doesn't move those.  I noticed that the #define's in general 
need some love.  There's quite a lot in kvm.h that's specific to vmx and 
there's a bit of asymmetry between vmx and svm (svm has kvm_svm.h, vmx 
used to but it was removed recently).  There's also a ton of unused 
#define's (quite a few that are typos).

I was planning on submitting a cleanup patch series today so I'll just 
fold the above changes into that.

>>
>> +static int nm_interception(struct kvm_vcpu *vcpu, struct kvm_run 
>> *kvm_run)
>> +{
>> +       spin_lock(&vcpu->kvm->lock);
>>   
>
> Why is the lock needed? everything below is vcpu-local AFAICS.

You're right, removed in attached patch.

>> @@ -1664,6 +1685,12 @@ static void svm_set_cr3(struct kvm_vcpu *vcpu, 
>> unsigned long root)
>>  {
>>      vcpu->svm->vmcb->save.cr3 = root;
>>      force_new_asid(vcpu);
>> + +    if (vcpu->fpu_active) {
>> +        vcpu->svm->vmcb->control.intercept_exceptions |= (1 << 
>> NM_VECTOR);
>> +        vcpu->svm->vmcb->save.cr0 |= CR0_TS_MASK;
>> +        vcpu->fpu_active = 0;
>> +    }
>>  }
>>  
>>  static void svm_inject_page_fault(struct kvm_vcpu *vcpu,
>>   
>
> Any numbers?  I use user/test/vmexit.c to test as it gives the highest 
> relative speedup.

Hard to say exactly because of the noise.  I did two runs of 4 test/vmexit:

Before 4091, 4194, 4559, 4439
After: 3979, 4324, 3918, 3910

So there's definitely a speedup, but probably only 100-200 cycles.

Regards,

Anthony Liguori